Electrical geophysics (IP/RS)
Electrical prospecting involves the detection of surface effects produced by electric current flow in the ground. There is much greater variety of techniques available than in the other prospecting methods, where one makes use of a single field of force or anomalous property- gravitation, magnetism, elasticity, radioactivity. Using electrical methods, one may measure potentials, currents, and electromagnetic fields that occur naturally- or are introduced artificially- in the earth. Furthermore, the measurements can be made in a variety of ways to determine a variety of results. Basically, however, it is the enormous variation in electrical conductivity found in different rocks and minerals that makes these techniques possible.
Electrical methods include self-potential (SP), telluric currents and magnetotellurics (MT), resistivity including mise-a-la-masse, electromagnetic (EM), including AFMAG, and induced polarization (IP). They are often classified by the type of energy source involved, that is, natural or artificial. On this basis the first three and AFMAG above are grouped under natural sources and the remainder as artificial. Such a classification can be made for prospecting methods in general. Hence gravity, magnetics, and radioactivity are included in the natural source methods, whereas seismic requires artificial energy.
Abilities and properties